A tough perennial with flat flower clusters whose shallow nectar feeds hoverflies, lacewings, and tiny parasitic wasps all summer.
Achillea millefolium · also called Common yarrow, Milfoil
Windows are counted from the average date of your last spring frost.
Yarrow is the most reliable insectary plant a home gardener can add: its wide flower heads hold hundreds of tiny florets that small beneficial insects can actually reach. It thrives on lean soil and little water.
A little history. Each flat head is a cluster of many small daisy-like flowers, so the shallow nectar sits within reach of short-tongued beneficial insects. Leaves are finely divided, giving a feathery outline.
Aim for 15 inches (40 cm) between plants once thinned. Press seed onto the surface and do not cover — it needs light. Mist daily so the top quarter-inch never dries. Seedlings emerge in 7–21 days.
Either works — needs 8 in soil depth and sharp drainage; spreads by runners in open beds. In containers: 3-gallon pot, wider rather than deeper.
Water weekly the first season, then only in long dry spells. Water when water when leaves look dull and the top 2 inches are dry. Aim for about 1 inch per week while establishing.
Once in early spring, or not at all on decent soil. What to use: a thin scatter of compost; skip high-nitrogen feed, which causes flopping.
Cut spent flower heads back to a side bud to bring a second flush. Shear the whole plant to 6 in after the main bloom if stems sprawl.
It's ready when cut flowers when most florets in a head are fully open and the color is firm — heads cut in tight bud dry papery and pale. Cut stems in mid-morning after dew dries, taking them low on the stem just above a set of leaves. Strip lower leaves at once so the stem stays clean for drying or the vase.
Fresh stems last 7–10 days in water. For dried use, bundle 8–10 stems and hang upside down in a dark, airy room for 2–3 weeks.
Not a succession crop. Shear after the first bloom and most plants rebloom in 4–6 weeks.
Leave a few inches of stem over winter as crown protection, then cut to the ground in early spring. Divide every 3 years to prevent a dead center.
Sea Buckthorn
Sea buckthorn wants the same lean, sharply drained, sunny ground yarrow prefers, and yarrow's long bloom draws in the hoverflies and lacewings that work over aphid colonies on the shrub's new shoots.
Hops
Hop bines are chronically troubled by aphids and spider mites. Yarrow planted at the foot of the trellis, outside the digging zone, gives predatory insects a nectar source all season so they stay near the bines.
Goji Berry
Goji tolerates the same dry, alkaline-leaning soil as yarrow, and yarrow's open florets bring in the lacewings and parasitic wasps that reduce the aphids clustering on goji's soft shoot tips.
Bee Balm
The pair covers two different guests: bee balm's tubular flowers draw bees and hummingbirds, while yarrow's shallow florets serve the small short-tongued insects that cannot reach into a tube. Give both good air movement, since each can get powdery mildew when crowded.
Elderberry
Elderberry blooms early and then offers nothing to beneficial insects. Yarrow flowering from early summer into fall keeps hoverflies and parasitic wasps on site, where they work over the aphids that curl elderberry shoot tips.
Stinging Nettle
Nettle hosts early-season aphids that feed the first generation of ladybugs and lacewings; yarrow then supplies the nectar those adults need to keep laying. Plant both in a contained edge patch, as each spreads by runners.
Lavender
Both want full sun, lean soil, and sharp drainage, and neither wants summer watering once rooted. Grouping them lets you keep a whole dry border on the same watering schedule while extending nectar supply for weeks.
Grape
Flowering ground cover in vineyard rows has been shown to support more predatory insects and parasitic wasps. Yarrow along the row edge fills that role without competing much with deep grape roots.
Fennel
Fennel's roots release compounds that stunt most garden neighbours, and a young yarrow clump is easily overtopped by it as well. Fennel's own flowers do feed hoverflies and tiny parasitic wasps, so keep it as a separate insectary patch well away from this one.
Peppermint
Mint runs underground faster than yarrow and will thread through and swamp the clump, making both impossible to lift cleanly. Keep mint in a sunken pot or a separate bed.
Lettuce
Yarrow spreads by shallow runners and shades low salad rows as it fills out, so it out-muscles lettuce for surface moisture and light. Keep it to a border rather than inside a salad bed.
An established yarrow clump colonises open ground with creeping stems and will crowd out slow, small seedlings before they get going. Site it at the bed edge or in its own strip where you can cut the runners back once a year.
A perennial — it holds its spot for years, so it sits outside the annual rotation.
Yarrow is a long-lived perennial, so it sits outside the annual rotation — give it a permanent border or strip rather than a bed you plan to till. It is a moderate feeder that adds no nitrogen, and there is no waiting period for any family that follows if you do remove it.
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